Exopolymeric substances (EPS) from Bacillus subtilis: polymers and genes encoding their synthesis

Bacterial exopolymeric substances (EPS) are molecules released in response to the physiological stress encountered in the natural environment. EPS are structural components of the extracellular matrix in which cells are embedded during biofilm development. The chemical nature and functions of these EPS are dependent on the genetic expression of the cells within each biofilm. Although some bacterial matrices have been characterized, understanding of the function of the EPS is relatively limited, particularly within the Bacillus genus. Similar gaps of knowledge exist with respect to the chemical composition and specific roles of the macromolecules secreted by Bacillus subtilis in its natural environment. In this review, the different EPS from B. subtilis were classified into four main functional categories: structural (neutral polymers), sorptive (charged polymers), surface-active and active polymers. In addition, current information regarding the genetic expression, production and function of the main polymers secreted by B. subtilis strains, particularly those related to biofilm formation and its architecture, has been compiled. Further characterization of these EPS from B. subtilis remains a challenge.